Earth's most important iron ore deposits are found in sedimentary rocks. They were formed from chemical reactions that combined iron and oxygen in marine and fresh waters. The two most important minerals in these deposits are iron oxides: hematite (Fe2O3) and magnetite (Fe3O4).
Nearly all of Earth's major iron ore deposits are in rocks that formed over 1.8 billion years ago. At that time Earth's oceans contained abundant dissolved iron and almost no dissolved oxygen. The iron ore deposits began forming when the first organisms capable of photosynthesis began releasing oxygen into the waters. This oxygen immediately combined with the abundant dissolved iron to produce hematite or magnetite. These minerals deposited on the sea floor in great abundance, forming what are now known as the "banded iron formations." The rocks are "banded" because the iron minerals deposited in alternating bands with silica and sometimes shale. The banding might have resulted from seasonal changes in organism activity.
Chalybeate, or mineral springs, is a term used when water is highly saturated with iron that precipitates out of solution forming an iron-rich stain along the surface of an outcrop. These iron-rich waters are in solution until reaching the surface, where the iron becomes oxidized, forming an iron coating along the water’s path. The different colors are a result of the different oxidation states of iron. At one time, these mineral springs were believed to have healing powers with many health benefits. Unfortunately, these springs simply leave you with a lingering iron taste with no health benefits, but do provide an aesthetically pleasing photo opportunity.
In the Garland County area of Arkansas spring waters can be divided into six general groups: Pure waters, Chalybeate, Lime, Chalybeate and Lime, Sulphur, and Copperas and Alum.
Pure waters are common among the mountains and issue from the novaculites or the overlying sandstones, being the surface waters which have percolated through the rocks of these formations.
Chalybeate springs are very common among the Novaculite Mountains, but commonly come from a particular part of the formation, the upper Ouachita horizon, also known as
the manganese and iron bed. This porous stratum is a great water channel and the springs issuing from it are much larger than pure water springs. The iron beds of these springs are probably derived from the limonite of this stratum. Chalybeate springs are also commonly found in the basins of rock underlying the novaculites, but they are not so plentiful in the overlying rocks. Chalybeate springs are noted at many places in the account of the detailed geology. Some are very large, for example the great spring at Crystal Springs, the Big Chalybeate near Hot Springs, and the Warm Spring in the eastern part of the Cossatot Mountains.
Lime waters – The limestone’s underlying the novaculite furnish hard waters in the districts where they approach the surface. Since the distribution of limestone is general hard spring waters are commonly found in the area.
Chalybeate and lime waters – Sometimes iron is present in these hard waters in sufficient quantity to produce the red deposit characteristic of chalybeate springs, and to give the taste of iron water.
Sulphur waters – Several springs of Sulphur water are known to be in this area. These springs have a strong odor and a strong sulphur taste with a white deposit.
Copperas and Alum waters – The copperas and alum waters come from the black shale’s of the lower graptolitic horizon. A few springs noted in these shale’s have sour waters, and wells dug in them are sometimes abandoned. The decomposition of small deposits of pyrites is probably the cause of their peculiarities.
In order to claim this earth cache email the answers to the following questions to rsmithfam411@gmail.com, please include the cache name and GC number with your email. Please do not post photos in your online log that will give any answers away.
Questions:
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What is a “banded iron formation?”
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What type of spring is located at the posted coordinates?
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What type of rock is normally associated with the spring located at the posted coordinates?
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